Fac-simile Scheda Linee di Ricerca - Federalimentare

Dati pubblicati inerenti il tema di ricerca:1. Pittia P., Sacchetti G., Rocculi P., Venturi L., Cremonini A., Dalla Rosa M. (2009). Waterstate and mobility affect mechanical properties of coffee beans. In Proceeding of 10thInternational Symposium on the Properties of Water ISOPOW 10 . CRC, Boca Raton, FL. InpressPlasticization and antiplasticization effect of water in raw and roasted coffee beans wereinvestigated and discussed considering water-matrix interactions as described by sorptionisotherms as well as water ‘freedom’ and mobility.Sorption isotherms were obtained in the 0.24 - 0.94 a w range and fitted by the GAB equation.Mechanical properties of samples equilibrated at different aw were studied by uniaxialcompression. Freezable water and water mobility were investigated by differential scanningcalorimetry (DSC) and Low Resolution Nuclear Magnetic Resonance (LW-NMR) through theanalysis of the transverse relaxation time (T 2 ). DSC and NMR results showed that the rehydrationprocess in coffee beans could be divided into two different stages. The first stage(a w from 0.24 ±0.01 up to 0.76 - 0.78 and to 0.86 for raw and roasted samples, respectively),where sorbed water acts as antiplasticizer with an increase of fracture force at increasingmoisture level, representing the solid matrix hydration. In the second stage, at increasinglevels of hydration (above a w 0.78 and 0.86 for raw and roasted samples, respectively), afterthe completion of the monolayer hydration, water behaves as a bulk-like agent as confirmedby the appearance of an endothermic melting peak and by a significant increase of T 2 . Only inthis stage water acts as a plasticizer. These results suggest that bulk-like water accounts for theplasticization effect as described by mechanical analysis.2. Pittia P., Sacchetti G. (2008). Antiplasticization effect of water in amorphous cell foods. Areview. Food Chemistry, 106: 1417–1427.Water is the most effective plasticizer in food matrices, decreasing glass transition temperature(Tg) and mechanical resistance and determining a softening effect with the increasing ofits concentration. However an opposite effect (i.e. hardening, toughening) could be observedin some food and in specific moisture or a w range and this is referred to an anti-plasticizationeffect. Several are the possible causes for this phenomenon and various are the factors thathave been recognized to affect its occurrence in a food matrix: mechanical testing method,mechanical parameter tested, type of food (composition and micro-macrostructure).In this paper, several studies on anti-plasticization effect of water are reviewed by focusing theattention on the interactions water–food matrix and in particular to those occurring in amorphouscell foods. The different chemical and physical factors that affect this phenomenon arealso discussed.The simultaneous occurrence of a plasticization and anti-plasticization effect of water, even ifin different a w range, and the results of studies on amorphous food matrices may suggest animportant effect of water–matrix interaction on the textural properties.SISTAL - SOCIETA’ ITALIANA DI SCIENZE E TECNOLOGIE ALIMENTARIDipartimento di Scienze e Tecnologie Agroalimentari, Università degli Studi della TusciaVia San Camillo de Lellis, 01100 ViterboTel.: 0761- 35 74 94/7 , Fax: 0761- 35 74 98, e-mail: mmoresi@unitus.it431